Light emitting device with improved electrode structure to minimize short circuiting

ABSTRACT

A light emitting device is disclosed which includes a semiconductor block, an active layer disposed in such a fashion as to penetrate through the mutually facing end surfaces of the semiconductor block, and an electrode disposed on the main plane of the semiconductor block, wherein the electrode consists of a first electrode portion disposed along the active layer, and a second electrode portion continuing integrally the first electrode portion and having the periphery thereof out of contact from the periphery of the second main plane of the semiconductor block. A current is caused to uniformly flow through the entire active layer, and a light emitting operation is carried out stably. Since the electrode is not disposed on the periphery of the semiconductor block, the occurrence of junction short-circuit, which might otherwise occur when a wafer is cut off to produce laser chips or when the corners of the chip break off, can be reduced.

BACKGROUND OF THE INVENTION

This invention relates to a light emitting device, and more particularlyto a semiconductor laser device.

A semiconductor laser chip as a light source for optical communicationor for data processing units such as digital audio disks, video disks,and so forth is discussed, for example, by Oka et al in the articleentitled "Innovation of Semiconductor Laser Technique" on page 25 of theMay issue of "Semiconductor World", 1982.

A prior art reference ("Semiconductor Laser Satisfying Requirements ofAudio Disks" by Fushiki et al in the September 14 issue of "NikkeiElectronics", p.p. 138-152) discloses that a semiconductor laser chip(which will hereinafter be referred to also as "laser chip") can beformed by cutting (causing cleavage) of a wafer having formed thereonelectrodes, with the electrode having a multi-layered metal structureusing mostly gold (Au) as its principal material.

The inventor of this invention has found out that when the wafer is cutto produce the laser chips, Au as the electrode is stretched and tornoff. Because of this, a part of the AU electrode hangs down in theproximity of the chip and often causes a junction short-circuit defect.

The inventor has also clarified that when the laser chip described aboveis produced, the electrode disposed on one surface of the laser chip islikely to swell out and to hang down for the following reasons, andhence a short-circuit is likely to develop around a p-n junction.

The laser chip has a structure in which a multi-layered grown layer isformed on a main plane of a substrate which is about 100 μm thick, andin which laser light is emitted from the end surface of an active layeras one of the constituent layers of the multi-layered grown layer (moreaccurately, the end surface of a resonator). At least one of theelectrodes is disposed on the side of the upper surface of themulti-layered grown layer. The distance between the electrode on themulti-layered grown layer and the active layer is extremely small, e.g.about 3 μm. Therefore, if the electrode on the multi-layered grown layerswells out and hangs down from the periphery of the laser chip, thehanging portion of the electrode comes into contact with a region of adifferent conductivity type while bridging the p-n-junction, or comesinto contact with the p-n junction itself, thereby causing an electricshort-circuit. Since the electrode on the multi-layered grown layer ismade of Au having high malleability as described already, Au isstretched and torn off when the wafer is cut, and an expanding electrodeportion is unavoidably formed around the periphery of the laser chip.

The inventor has also clarified that the corners of the laser chip arelikely to crack, and a short-circuit can also develop due to such acrack.

SUMMARY OF THE INVENTION

The present invention is therefore directed to provide a novel lightemitting device having high production yield and high reliability.

Among the inventions disclosed herein, the following is a typicalexample.

In the light emitting device in accordance with the present invention,an anode electrode portion is not extended around the periphery of thelaser chip, except at a portion corresponding to the end surface of aresonator which emits the laser light, in order to prevent theoccurrence of a short-circuit due to the hanging electrode. The cornersof the anode electrode corresponding to the corners of the laser chipcan be chamfered so that they are positioned further away from thecorners of the laser chip. Even if the corners of the laser chip undergobreakage when the wafer is scribed and cracked to provide the laserchips, the probability that the crack portion reaches the anodeelectrode portion is extremely low because the corners of the laser chipare chamfered as described above. In consequence, hang-down of theelectrode due to cracks of the corners of the laser chip can beprevented, and the ratio of occurrence of short-circuits due to thehanging electrode portion can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a laser chip in accordance with a firstembodiment of the present invention;

FIG. 2 is a perspective view of a laser chip in accordance with a secondembodiment of the present invention;

FIG. 3 is a schematic view showing the state of exothermy under thestate in which the laser chip is actually mounted;

FIG. 4 is a schematic plan view showing also the state of exothermyunder the state in which the laser chip is actually mounted;

FIG. 5 is a diagram showing the relation between the width of a neckportion of an anode electrode corresponding to the end portion of aresonator and a current density;

FIG. 6 is a perspective view showing the state under which a corner ofthe laser chip shown in FIG. 1 breaks off and short-circuit develops dueto the breakage;

FIG. 7 is a perspective view showing a laser chip in accordance with athird embodiment of the present invention;

FIG. 8 is a sectional view of a wafer in one production process of a BHtype semiconductor laser chip in accordance with still anotherembodiment of the present invention;

FIG. 9 is a sectional view of the wafer after etching has been appliedthereto;

FIG. 10 is a sectional view of the wafer after burying and growingtreatment has been applied thereto;

FIG. 11 is a sectional view of the wafer after a part of the buriedgrown layer has been removed; and

FIG. 12 is a sectional view of the wafer after an insulating film and anelectrode have been formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a perspective view of a laser chip in accordance with a firstembodiment of the invention, FIG. 3 is a schematic view showing thestate of exothermy under the state in which the laser chip is actuallymounted, FIG. 4 is a schematic plan view showing also the state ofexothermy of the laser chip and FIG. 5 is a diagram showing the relationbetween the neck portion of an anode electrode corresponding to the endportion of a resonator and a current density.

This embodiment illustrates an example in which the present invention isapplied to a long wave semiconductor laser chip of a buriedheterostructure (BH).

Laser chips are produced by cutting a compound semiconductor wafer, onwhich chips have been formed, by cleavage, scribing, cracking and thelike, in longitudianl and transverse directions in the grid form. Thelaser chip in this embodiment is characterized by the pattern of ananode electrode which is disposed at a position as close as from 3 to 4μm to a resonator, as shown in FIG. 1. This electrode pattern can befreely changed by selecting a suitable mask pattern for evaporation andetching to be used for producing the electrode.

The structure of the laser chip will be first described before thecharacterizing feature of this electrode pattern is described.

A multi-layered grown layer is produced by first forming a buffer layer5 made of n-type In-P on a main plane of a substrate 4 made of n-typeIn-P (the upper surface: (100) crystal plane), after which an activelayer (resonator) 6 made of In-Ga-As-P, a cladding layer 7 made ofp-type In-P and a cap layer 8 made of p⁺ -type InGaAsP are formed instrip on the buffer layer 5. This multi-layered grown layer has across-sectional shape of an inverted triangle, and forms a so-calledinverted mesa structure. The side surface of this inverted mesastructure is a (111) crystal plane on which In appears. The portionbelow the lower end of this inverted mesa plane portion is a forwardmesa structure which expands gently. A blocking layer 9 made of p-typeInP, a buried layer 10 made of n-type InP and a cap layer 11 made ofInGaAsP are buried in the laminate state on each side of thismulti-layered grown layer. The main surface portion of the multi-layeredgrown layer on the side of the substrate 4 except the electrode contactregion is covered with an insulating film (SiO₂ film) 12. The anodeelectrode 3 consisting of an Au type electrode is formed on the mainsurface side of the substrate 4.

A cathode electrode 13 of an Au type is disposed on the reverse of thesubstrate 4. Zinc (Zn) is diffused into the surface layer portion of thecap and cladding layers 8 and 7, thereby forming an ohmic contact layerconsisting of a p⁺ -type Zn diffusion region.

The laser chip 1 is, for example, 400 μm wide (L₀), 300 μm long (L₁) and100 μm high (L₂), and the active layer 6 is about 2 μm wide and about0.15 μm thick.

Next, the characterizing feature of the electrode structure will bedescribed.

As can be seen from FIG. 1, the anode electrode 3 is not disposed overthe entire upper surface of the laser chip 1. The anode electrode 3extends on the peripheral portion of the laser chip 1 corresponding tothe end portion of the resonator 6, but the other peripheral portions ofthe anode electrode 3 are recessed by a distance of L₃, L₄ (e.g. L₃ =L₄=50 μm) from the periphery of the laser chip 1. In a preferredembodiment, the width W of the electrode 18 (neck width) on the endportions of the resonator covering the end portions is 100 μm, and thelength L₅ of the anode electrode 3 extending along the resonator at theportion other than on the resonator is 200 μm.

Since the anode electrode 3 is not disposed around the periphery of thelaser chip 1, the electrode 3 is prevented from hanging down on the sidesurfaces of the chip 1 at the time of scribing. Since the anodeelectrode 3 is disposed over the entire length of the active layer(resonator) 6, on the other hand, the carrier injection efficiency aswell as the light emitting efficiency do not drop near the end surfacesof the resonator, and the occurrence of self-excitation pulseoscillation (pulsation) can also be prevented.

The dimension of the anode electrode 3 is designed in consideration ofheat radiation at the time of driving the laser and for the purpose ofsecuring a sufficient area for connecting the bonding wire.

First, exothermy at the time of driving the laser will be examined. Ascan be understood from the temperature distribution shown in FIG. 4,heat resistance is great at the end surface portions of the resonator ofthe laser chip 1 and range of temperature rise is great. Specifically,the hatched region in FIG. 4 represents a high temperature region, andits contour represents an isothermal line. Almost all the heat generatedat the portion of the resonator 6 in the laser chip 1 escapes to asupport 21 through the substrate 4 and a solder 20 as indicated by anarrow in FIG. 3. However, when the laser is operated at a high current,the heat that escapes by convection or radiation through the electrode 3on the end portions of the resonator, which is spaced apart from theresonator 6 by about 3 to 4 μm, cannot be neglected. The width a of thehigh temperature region is about 100 μm as shown in FIG. 4, and the neckwidth W of the electrode 18 on the end portions of the resonator must beat least 100 μm in response to the width a in consideration of the heatradiation efficiency. If the neck width W becomes greater, however, thecut width of the anode electrode 3 when the wafer is cut off becomesgreater, so that the projecting portion of Au that is torn off willbecome greater, and the probability of short-circuit will become alsogreater. For this reason, the neck width is preferably as small aspossible. Therefore, the neck width W of the electrode 18 on the endportions of the resonator is prescribed to be 100 μm.

The neck width W of the electrode on the end portions of the resonatoris also associated greatly with electromigration. The redundancy ofelectromigration is represented by a diagram whose ordinate represents acurrent density J (A/cm²) and whose absciassa represents the neck widthW (μm), as shown in FIG. 5. Its curve is given by the followingequation: ##EQU1## where I_(max) is a maximum allowable current, W isthe neck width, t is the thickness of the electrode, L₁ is the length ofthe resonator, and L₅ is the length of the peripheral electrode alongthe resonator.

The dotted line in the diagram represents an allowable current density(6×10⁵ A/cm²) of Au. The neck width W is 100 μm in view of the heatradiation effect as described above. Therefore, the thickness t of theanode electrode 3 is determined to be 0.6 μm by putting the values W=100μm and I_(max) =6×10⁵ A/cm² into equation (1).

The distance L₃, L₄ between the periphery of the anode electrode and theperiphery of the chip is decided to be 50 μm in view of the fact that asufficient area is necessary for connecting a bonding wire.

The pattern dimension of the electrode is determined in the mannerdescribed above.

As described above, the present invention is characterized in that theelectrode 3 consists of the first electrode portion (width W) extendingon the active layer 6 and the second electrode portion connectedintegrally to the first electrode portion and having the peripherythereof out of contact from the periphery of the main surface of thelaser chip.

Embodiment 2

The characterizing feature of a second embodiment of the presentinvention is that chamfer portions 19 are formed at the four corners ofthe anode electrode 3, as shown in FIG. 2.

Even if the electrode 3 is recessed from the periphery of the laser chipas in the first embodiment, a hang-down portion 16 will occur from theAu electrode 3 if the corner portion or portions of the laser chip breakoff, and will result in the junction short-circuit.

If the chamfer portions 19 are disposed on the anode electrode 3 (thesecond electrode portion), the probability of occurrence of such ashort-circuit can be reduced. The chamfer length C is decided to be 30μm, for example, in order to reduce the probability that a crack at thecorner portion extends to the anode electrode 3.

Even when the corners of the rectangular laser chip 1 breaks off fromtime to time, the probability that the crack reaches the anode electrodeportion 3 is extremely low because the corners of the laser chip 1 arechamfered. Therefore, the electrode does not hang down even when anycrack reaching the electrode portion 3 occurs due to the crack of thecorners of the laser chip 1, and the ratio of occurrence ofshort-circuits due to the hanging electrode portion can be reduced.

The foregoing two embodiments of the invention provide the followingeffects.

(1) In the light emitting device of the present invention, the anodeelectrode portion does not extend around the periphery of the laser chipexcept the peripheral portion of the laser chip that corresponds to theend portion of the resonator emitting the laser light. Therefore, theoccurrence of a short-circuit caused by the hanging Au electrode, thatis formed at the time of scribing, can be prevented. In the secondembodiment, in particular, since the corner portions of the anodeelectrode corresponding to the corners of the rectangular laser chip arechamfered and are further spaced apart from the latter, the probabilityis extremely low that those crack portions of the corners of the laserchip, which may occur upon scribing and cracking of the wafer to producethe laser chips, reach the anode electrode portion. Because the anodeelectrode portion does not break off as described above, the electrodedoes not hang down due to the crack of the corners of the laser chip,and the ratio of occurrence of short-circuits due to the swellingelectrode portions can be reduced.

(2) When forming the anode electrode 3 of the laser chip 1 of thepresent invention, the electrode pattern can be formed by changingeither the pattern of an evaporation mask or the pattern of an etchingmask. Therefore, the production cost does not rise, and no troubleoccurs even when the chip structure is changed.

(3) The effect (1) improves the production yield when cutting off thewafer to obtain the laser chips 1, and the production cost can bereduced consequently.

(4) The semiconductor laser chip in accordance with the presentinvention can reduce the occurrence of defects relating to theappearance such as the electrode extending on the peripheral surface ofthe laser chip; hence the production yield can be improved.

Embodiment 3

FIG. 7 is a perspective view of a BH type semiconductor laser chip inaccordance with a third embodiment of the present invention, and FIGS. 8through 12 are sectional views of the BH type semiconductor laser chipduring its production process.

This embodiment is characterized in that buried layers 700 and blockinglayers 600 that interpose an active layer 300 from both of its sides arelocally disposed on a substrate 100, as shown in FIG. 7. Besides theeffects brought forth by the first and second embodiments, thisembodiment provides the following effects.

In the semiconductor laser chip of this embodiment, the portions of theburied regions spaced apart from the active layer are removed, thelength of an exposed p-n junction is small, and most of the periphery ofthe anode electrode is recessed inward by dozens of microns from theperiphery of the insulating film. Therefore, degradation of thewithstand voltage and short-circuits are not likely to occur even whenforeign matter is deposited or the hanging electrode material develops,and both production yield and reliability can be improved.

The wire connection portion of the semiconductor laser chip inaccordance with the present invention is arranged above the substratewhere laser oscillation is not effected. Therefore, even when wirebonding is conducted, the chip characteristics do not deteriorate. Onthe contrary, the chip characteristics become high quality, and theproduction yield can be improved.

Next, the production process of the semiconductor laser chip will beexplained briefly.

First of all, a compound semiconductor substrate 100 is prepared asshown in FIG. 8. This substrate is made of n-type InP. A multi-layeredgrown layer 1600 consisting of a buffer layer 200 of n-type InP, anactive layer 300 of InGaAsP, a cladding layer 400 of p-type InP and acap layer 500 of p-type InGaAsP is formed on the (100) crystal plane ofthe substrate 100 by the liquid epitaxial method. The buffer layer 200,the active layer 300 and the cladding layer 400 form a doubleheterostructure. The substrate is about 200 μm thick, the active layer 3is 0.15 μm thick and the rest of layers are from about 1 to about 2 μmthick.

Next, an insulating film (SiO₂) is formed on the main plane (uppersurface) of a wafer 1500 by chemical vapor deposition (CVD) as shown inFIG. 9, and this insulating film is partially removed byphotolithography to form a large number of stripe-like masks 1700, whichare from 5 to 6 μm wide, in a direction parallel to the direction of<110> cleavage. Thereafter, the semiconductor layer of the wafer 1500exposed from the masks 1700 is etched by an etching solution such asbromoethanol. Etching is conducted in such a manner as to reach theintermediate depth of the buffer layer 200 or the surface layer portionof the substrate 100. In this embodiment, etching reaches theintermediate depth of the buffer layer 200. The upper portion of theactive layer 300 covered with the masks 1700 becomes the inverted mesastructure exhibiting an inverted triangular cross-section as a result ofanisotropic etching, and remains in the stripe form along the <100>direction of the crystal. The portion below the active layer 300 formsthe forward mesa portion describing curves. The mask space is about 400μm.

Next, the masks 1700 extending partially on the main surface of thewafer 1500 are removed. Then, a blocking layer 600 of p-type InP, aburied layer 700 of n-type InP and a cap layer 800 of n-type InGaAsP aresequentially buried into the portion that is recessed by etching, by theepitaxial method as shown in FIG. 10. These three layers will sometimesbe called merely "the buried layer" in this specification.

When the laser chips of the first and second embodiments are produced,an insulating film such as 12 shown in FIGS. 1 and 2 is formed onportions of the upper surface other than over the inverted mesa, andthen electrodes having a desired shape are formed on both main planes ofthe laser chip. The wafer is then cut off to obtain the laser chips.When the laser chip of the third embodiment is produced, the followingprocess is carried out.

The portion of the buried layer apart from the active layer, that is,the intermediate portion of the active layers 300 of two laser chips, isremoved by photolithography technique, as shown in FIG. 11. A mesaportion which is about 100 μm wide with the mesa portion being thecenter is formed. To completely remove the portion of the buried layerto be removed, the removing operation is carried out so as to reach thesurface layer portion of the substrate 100. This step forms only thenecessary portion for emitting the light on the semiconductor substrate.

Next, an insulating film 1000 consisting of SiO₂ or the like is formedpartially on the main plane of the wafer 1500. Therefore, the ends ofp-n junction exposed from the side surfaces are covered with thisinsulating film 1000. The insulating film 1000 is not disposed in thecut-off region in a direction crossing the cleavage plane of the wafer1500 at right angles (the scribe area represented by a width a) and onthe surface layer portion of the inverted mesa portion, as shown in FIG.12. Next, zinc (Zn) is introduced into the main plane of the wafer 1500using the insulating film 1000 as the mask, and a Zn diffusion layer 9reaching the intermediate depth of the cladding layer 400 is formed.This Zn diffusion layer 900 functions as an ohmic layer of a contactelectrode. An anode electrode 1100 is disposed on the main plane of thewafer 1500 and a cathode electrode 1200, on its reverse. Though thecathode electrode 1200 is disposed on the entire reverse surface of thewafer 1500, the anode electrode 1100 is disposed at the portions otherthan the entire portion of the mesa portion 1800 (i.e. the end portionsof the mesa where light is emitted are, of course, left uncovered) andother than the peripheral portions of the insulating film 1000 placeddirectly on the substrate 100 (the region which is dozens of micronswide from the periphery of the insulating film, exclusive of theportions in the proximity of the mesa portion 1800). This means that theanode electrode 1100, too, is disposed as a stripe pattern havingequidistance contracted portions on the main plane of the wafer 1500.The line direction connecting these contracted portions is the cleavageplane. The reverse of the wafer 1500 is etched before the cathodeelectrode 1200 is disposed thereon, and the wafer 1500 is about 100 μmthick as a whole.

Next, external force is applied to one end portion of the wafer 1500 bya diamond tool or the like, and a scratch for cleavage is equidistantlyformed along the cleavage plane of the crystal. External bending stressis then applied to the wafer 1500 to effect cleavage, and rectangularslices are obtained. Scribes are formed in a scribe area of the slice bya diamond tool or the like in a direction crossing the cleavage line atright angles, and the slices are cut by cracking along the scribes,thereby forming a large number of laser chips.

A view of the laser chip 1900 of the third embodiment after theindividual chips have been separated can be seen in FIG. 7. Thedimensions are, for example, 400 μm wide, 300 μm long and 100 μm deep.When a predetermined voltage is applied across the anode electrode 1100and the cathode electrode 1200, the end surface of the active layer (themirror surface) which is 300 μm long oscillates the laser light 2000.The laser chip is used while being fixed to a support via either theanode electrode 1100 or the cathode electrode 1200 in practice. When,for example, the laser chip is fixed to a support made of high thermalconductivity SiC ceramic (thermal conductivity: 25 W/deg.cm) via asolder, the cathode electrode 1200 can be used as the fixing surface,and the wire 2100 can be connected to the anode electrode 1100 which isdirectly placed on the substrate 100. In this case, the impact at thetime of wire bonding is applied to the substrate 100 which hardlyaffects the chip characteristics, and does not affect the active region(consisting of the active layer 300 and the blocking layer 600) whichoscillates the laser. It is therefore possible to prevent thedegradation of the laser chip characteristics by wire bonding when wirebonding is carried out.

Although the invention has been described in conjunction with specificlaser structures, it is to be understood that the particular teachingsregarding the anode electrode structure could be used in conjunctionwith other laser structures to obtain the aforementioned advantages. Asan example of another laser structure which could be used, attention isdirected to U.S. Ser. No. 712,028 of Masaaki Sawai, filed on even dateherewith and entitled "Semiconductor Laser Chip", which is herebyincorporated by reference.

Also, although particular dimensions have been given in the description,it is to be understood that these are for purposes of example, and canbe modified without departing from the scope of the present invention.

It is to be understood that the above-described arrangements are simplyillustrative of the application of the principles of this invention.Numerous other arrangements may be readily devised by those skilled inthe art which embody the principles of the invention and fall within itsspirit and scope.

What is claimed is:
 1. A light emitting device comprising:(1) asemiconductor block consisting essentially of:(a) a first main plane;(b) a second main plane facing said first main plane; (c) a first endsurface interposed between said first and second main planes; (d) asecond end surface facing said first end surface and interposed betweensaid first and second main planes; (e) a first side wall interposedbetween said first and second main planes and said first and second endsurfaces; (f) a second side wall facing said first side wall andinterposed between said first and second main planes and said first andsecond end surfaces; and (g) a light emitting region having one of theends thereof exposed on said first end surface and the other end thereofexposed on said second end surface, wherein said second main surface hasa periphery including end peripheral edges at intersections of saidsecond main surface and said first and second end surfaces and sideperipheral edges at the intersections of said second main surface andsaid first and second side walls; and (2) an electrode consistingessentially of:(a) a first electrode portion disposed on said secondmain plane of said semiconductor block along said light emitting region,and having the width thereof greater than the width of said lightemitting region; and (b) a second electrode portion disposed on saidsecond main plane of said semiconductor block, connected completelyintegrally with said first electrode portion, and having a peripherythereof recessed along said second main plane to be out of contact fromboth the end peripheral edges and the side peripheral edges of theperiphery of said second main plane.
 2. A light emitting deviceaccording to claim 1, wherein the portions of said second electrodeportion in the proximity of the corners of said semiconductor block arechamfered.
 3. A light emitting device according to claim 1, wherein abonding wire is connected to said second electrode portion.
 4. A lightemitting device according to claim 1, wherein said first electrodeportion has a length substantially equal to that of said light emittingregion.
 5. A light emitting device according to claim 4, wherein theportions of said second electrode portion in the proximity of thecorners of said semiconductor block are chamfered.
 6. A light emittingdevice according to claim 4, wherein a bonding wire is connected to saidsecond electrode portion.
 7. A light emitting device according to claim4, wherein said width of said first electrode portion is set to besubstantially equal to or greater than the width of a high temperatureregion generated along said first main surface by operation of saidlight emitting region.
 8. A light emitting device according to claim 1,wherein said first electrode portion has end peripheral edges extendingto the end peripheral edges of said second main surface.
 9. A lightemitting device according to claim 1, wherein said second electrodeportion is laterally shifted along said second main surface to be awayfrom said light emitting region.
 10. A light emitting devicecomprising:a substrate having first and second main surfaces facing oneanother; a convex portion formed to protrude from a portion of saidfirst main surface of said substrate, said convex portion comprising:(1)a buffer layer formed on said substrate; (2) an inverted mesa structureincluding an active light emitting layer formed on said buffer region, acladding layer formed over said active light emitting layer and a firstcap layer formed over said cladding layer, said inverted mesa structurehaving first and second end surfaces facing one another from which lightfrom said active light emitting layer is to be emitted and first andsecond sidewalls facing one another and interposed between said firstand second end portions of said mesa structure; and (3) a multi-layeredstructure comprised of a blocking layer, a buried layer and a second caplayer formed on said buffer layer to enclose said first and secondsidewalls of said inverted mesa structure, wherein said convex portionhas first and second end portions facing one another and correspondingto the first and second end portions of said inverted mesa structure,and wherein said convex portion further includes first and secondsidewalls facing one another and interposed between said first andsecond end portions of said convex portion, said first and secondsidewalls of said convex portion being formed by said multi-layeredstructure; an insulating layer formed to extend over said first mainsurface of said substrate, and also to extend over the first and secondsidewalls of said convex portion and over the second cap layer, saidinsulating layer leaving exposed the first and second end portions ofsaid convex portion and the first cap layer; an anode electrode formedto include:a first anode electrode portion formed on said first caplayer and on the insulating layer formed on the second cap layer and onthe first and second sidewalls of said convex portion; and a secondanode electrode portion connected integrally with said first anodeelectrode portion and formed on said insulating film formed over saidfirst main surface of said substrate, said second electrode portionhaving a periphery thereof recessed along said first main surface ofsaid substrate to be out of contact with the periphery of said firstmain surface of said substrate; and a cathode electrode formed on saidsecond main surface of said substrate.
 11. A light emitting deviceaccording to claim 10, wherein said first anode electrode portion has alength substantially equal to the length of said active layer.
 12. Alight emitting device according to claim 10, wherein the portions ofsaid second electrode portion in the proximity of the corners of saidsemiconductor block are chamfered.
 13. A light emitting device accordingto claim 10, wherein a bonding wire is connected to said secondelectrode.
 14. A light emitting device according to claim 11, whereinthe portions of said second electrode portion in the proximity of thecorners of said semiconductor block are chamfered.
 15. A light emittingdevice according to claim 11, wherein a bonding wire is connected tosaid second electrode portion.